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Chromosome mediated gene transfer of drug resistance to mitoxantrone
L A Hazlehurst1, P Gros, W S Dalton
1Moffit Cancer Center and Research Institute, University of South Florida, Tampa, USA.
Abstract:
The anthracenedione, mitoxantrone, frequently selects for a unique drug resistance phenotype that is not mediated by either MDR 1, MRP, or altered DNA topoisomerase II. In this study, we demonstrate that mitoxantrone resistance is likely to be multifactorial with at least one resistance mechanism being the result of a dominant genetic event. This finding was demonstrated by conducting chromosome transfer experiments from human breast cancer cell lines that were either sensitive (MCF7/S) or resistant to mitoxantrone (MCF7/Mitox). Chromosomes transferred from MCF7/Mitox cells into CHO-K1 cells resulted in the isolation of multiple clones resistant to mitoxantrone. In contrast, chromosomes transferred from the drug sensitive MCF7/S, parent cell line did not confer drug resistance in the rodent CHO-K1 recipient cell line. Both Alu-PCR analysis and Southern blot analysis demonstrated human DNA in the CHO-K1 cells receiving chromosomes from the MCF7/Mitox cells. Unlike the MCF7/Mitox cell line, the drug resistant, CHO-K1 chromosome transferrant clones did not have a decrease in total drug accumulation. We conclude that chromosome transfer from the MCF7/Mitox cell line into CHO-K1 cells, confers a non-transport mediated mechanism of drug resistance that is a dominant genetic event. These studies provide evidence of the genetic multifactorial nature of multidrug resistance in cells selected with mitoxantrone in-vitro.
Insights
Mitoxantrone resistance in cancer cells involves a dominant genetic event, not typical drug efflux pumps. Chromosome transfer experiments revealed a novel, non-transport mediated resistance mechanism.
Area of Science:
- Cancer Biology
- Genetics
- Pharmacology
Background:
- Mitoxantrone (anthracenedione) induces a unique drug resistance phenotype.
- This resistance is not explained by MDR1, MRP, or DNA topoisomerase II alterations.
Purpose of the Study:
- To investigate the genetic basis of mitoxantrone resistance.
- To determine if mitoxantrone resistance is multifactorial and involves dominant genetic events.
Main Methods:
- Chromosome transfer experiments using mitoxantrone-sensitive (MCF7/S) and resistant (MCF7/Mitox) human breast cancer cell lines.
- Transfer of chromosomes from MCF7/Mitox into CHO-K1 cells to assess resistance acquisition.
- Alu-PCR and Southern blot analysis to confirm human DNA presence in recipient cells.
- Measurement of total drug accumulation in resistant clones.
Main Results:
- Chromosome transfer from MCF7/Mitox cells conferred mitoxantrone resistance to CHO-K1 cells.
- Human DNA was detected in resistant CHO-K1 recipient cells.
- Resistant clones did not exhibit decreased drug accumulation, indicating a non-transport mechanism.
- Chromosome transfer from sensitive MCF7/S cells did not confer resistance.
Conclusions:
- Mitoxantrone resistance is likely multifactorial, involving a dominant genetic event.
- A non-transport mediated mechanism of drug resistance was conferred by chromosome transfer.
- These findings highlight the complex genetic nature of in-vitro mitoxantrone-selected multidrug resistance.